The temperature of battery cells in a battery system has a great influence on the power output, on the operational reliability and the operational life of a battery. It is possible by ascertaining the temperature of individual battery cells to counteract with the aid of cooling/heating devices any events where an upper and lower desired limit value of the temperature for the operation of the battery cells is exceeded or not achieved.
In order to ascertain reliable temperature measured values, it is necessary to measure the temperature of the battery cells at particular time intervals, wherein in order to obtain reliable measured data the temperature of the battery cells is always to be ascertained at the same predetermined positions.
Diodes, for example, may be used as sensor elements that are suitable for monitoring the temperature of battery cells. Alternatively, it is also possible to use transistors that are connected as diodes. The sensor elements are mainly embodied as NTC resistors or PTC resistors.
When using the abovementioned types of sensors, problems frequently occur with transferring heat between the battery cells and the sensor elements.
German Patent Publication No. DE 10 2005 058 315 A1 discloses a measuring method that uses an infrared sensor or a thermal imaging camera to sense and ascertain the battery or accumulator surface locally at different measuring points that are spaced apart. The infrared sensor may be moved along different scan paths and/or scan curves relative to the battery or accumulator surface being measured, or individual measuring points may be selected electronically from a thermal image in accordance with a predetermined pattern. The greater the number of measuring points and the more complex the scan paths and/or measuring point pattern, the more accurate are the conclusions relating to the temperature distribution and the more accurate are the conclusions relating to the battery or accumulator condition.
The infrared sensor disclosed in DE 10 2005 058 315 A1 may be embodied, for example, as a thermal imaging camera that records the temperature distribution over the entire battery surface in one measuring step. Selected measuring points are then used for evaluation purposes. Alternatively, the battery or accumulator surface may also be scanned using a spot-measuring infrared sensor, in that either the infrared sensor or the substrate of the battery measuring place is motorized and as a consequence is moveable so that it is possible by way of the motorized arrangement to move along different scan paths. Furthermore, multiple passes through the measuring point raster are possible in one scanning process in order to be able to better filter out deviations in the statistical measured values of an individual measurement or to be able at least to compensate for such deviations by way of forming an average.
The devices and method disclosed in DE 10 2005 058 315 A1 are suitable for performing tests on test benches and in laboratories. Due to the installation position and the constricted space conditions for example in a motor vehicle, the temperature of a plurality of battery cells of a battery module or of a battery system may only be monitored in a reliable non-contact manner in the manner described in the prior art with a high technical outlay and high costs.